1. Field of the Invention
The present invention relates generally to read head portions of magnetic heads for hard disk drives, and more particularly to lead overlaid read heads having magnetically pinned passive regions.
2. Description of the Prior Art
One well known way to increase the performance of hard disk drives is to increase the areal data storage density of the magnetic hard disk. This can be accomplished by reducing the written data track width, such that more tracks per inch can be written on the disk. To read data from a disk with a reduced track width, it is also necessary to develop sufficiently narrow read head components, such that unwanted magnetic field interference from adjacent data tracks is substantially eliminated.
The standard prior art read head elements include a plurality of thin film layers that are deposited and fabricated to produce a GMR read head, as is known to those skilled in the art. Significantly, where the width of the thin film layers that comprise the GMR read head is reduced below certain values, the magnetic properties of the layers are substantially compromised. To overcome this problem, GMR read heads have been developed in which the thin film layers have an ample width and the electrical leads are overlaid on top of portions of the thin film layers. This lead overlaid configuration has the effect of creating an active read head region having a width that is less than the entire width of the deposited layers, such that the magnetic properties of the thin film layers can be preserved. Thus, in the lead overlaid GMR read heads of the prior art, active magnetic layer portions exist between the electrical leads and passive magnetic layer portions exist beneath the electrical leads.
A problem that has been recognized with regard to such prior art lead overlaid read heads is that the passive region of the magnetic layers of the read head, and particularly the free magnetic layer, is not entirely passive. That is, external magnetic fields, such as from adjacent data tracks, create magnetic field fluctuation and noise within the passive regions of the free magnetic layer beneath the electrical leads. Thus, noise and side reading effects continue to be a problem with lead overlaid GMR read heads. The present invention seeks to solve this problem by pinning the magnetization of the free magnetic layer in the passive regions beneath the overlaid electrical leads, thus stabilizing the passive regions, and reducing noise and side reading effects.
The present invention is an improved magnetic head for a hard disk drive including a lead overlaid read head component in which the magnetic fields of the passive region of the free magnetic layer regions are pinned. In one embodiment of the present invention an additional thin film layer composed of a magnetic material such as the hard bias layer material is deposited on top of the free layer of the GMR head in the passive region beneath the overlaid electrical leads. When the hard bias layer is magnetically initialized, magnetic fields created in the new thin film layer act to pin the magnetic fields in the passive regions of the free layer. The operational characteristics of the read head are improved because the passive region of the free layer is magnetically pinned and thus not affected by side reading magnetic fields from adjacent data tracks. Noise and side reading effects are thereby reduced and the performance of the read head is thereby improved. In alternative embodiments of the present invention the passive region of the free layer is anti-parallel coupled through the deposition of a thin film ruthenium layer followed by a thin film magnetic layer on top of the passive region of the free layer. The anti-parallel coupled magnetic field within the passive region of the free layer is thereby rendered less sensitive to side reading and noise, such that an improved magnetic head is thereby produced.
It is an advantage of the magnetic head of the present invention that a lead overlaid read head has been developed with reduced noise and side reading problems.
It is another advantage of the magnetic head of the present invention that a lead overlaid read head has been developed having pinned magnetic fields in the passive region of the free magnetic layer thereof.
It is an advantage of the hard disk drive of the present invention that it includes a magnetic head having a reduced read track width with reduced side reading and noise.
It is another advantage of the hard disk drive of the present invention that it includes a magnetic head having a lead overlaid read head having pinned magnetic fields in the passive region of the free magnetic layer thereof.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description with makes reference to the several figures of the drawings.